Have you actually timed when the bisquettes are advancing, or are you just going by what the bisquettes look like after they have been pushed off the burner?

If you haven't timed when the bisquettes cycle through, I would do that first. Just to verify what is the time cycle when the bisquette advances. What I do is I will advance the a bisquette, set a kitchen timer for 18 minutes, then go off to do what I need to do. When the alarm goes off I will check if the bisquette had already advance, if it did, I will repeat the procedure but set the timer for 10 minutes. If the bisquette did not advance, I would time how long it will be for it to cycle. Fortunately I have a countdown feature on my timer, so that keeps track of the time past 18 minutes.

Though it doesn't appear you have had this problem in the past, a few things can come into play, that will effect how the bisquettes burn. The two most common is cold smoking, and/or humidity. When you are cold smoking; especially in your case - where you are using refrigeration; the lack of heat from the heating element can cause the bisquette not to fully burn. Humidity is another. If you haven't stored the bisquettes to prevent them from absorbing moisture, or if it is very humid during the time you are smoking, that can cause them to burn poorly.

Less common problems can be not enough power (voltage) getting to the generator. The bisquette burner should reach a temperature of around 550°F at the surface. You can test the temperature if you have an infrared thermometer. Sometimes the bisquettes come from the factory more compressed, then the previous ones you have been using. That can also cause the bisquettes to burn the way they are doing.